Hi @cling@bluebellgroup.com ,
Thanks for posting your question to the Community and hope to provide some info!
You are correct in the sense that there is something you can alter within the data feeds to include the 10% tax to your product prices. You could apply this 10% tax within your product feed backend. This way when the product block pulls in any products from the catalog automatically, the price will always show as whatever is listed in the feed, in this case your base price +10%.
Another option would be to manually select the products within a product block and define a static price while including the 10% tax beforehand.
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The image shows where to edit price in a product block!
Hope this helped and thanks for being a part of the Community!
Alex